Cathode ray apparatus



April 1938. K. scHLESINGER 2,114,611

' CATHODE RAY APPARATUS Filed Oct. 12, 1933 Jm/enfor:

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Patented Apr. 19, 1938 UNlTED STTS Application October 12, 1933, Serial No. 693,304 In Germany October 17, 1932 8 Claims.

The object of the invention is an arrangement for avoiding the cross-current error in Braun tubes. Under the term cross-current error there is understood in Braun tubes the error which leads to a distortion of the image, arising from the fact that the current of electrons consisting of electrons which are attracted towards the positive deflecting plate produces at the resistance of the plate circuit a drop in potential, which becomes added to the actual control potential and accordingly varies the actual value of the control potential in uncontrollable fashion.

According to the invention, the electron projecting anode and the deflecting plates are an ranged in such fashion geometrically in relation to each other that the undeflected ray passing through the anode would touch against the controlling defiecting plate, or preferably meet against the same, approximately at the centre thereof. The controlling deflecting plate (referred to in the following as the control plate) is furnished, in accordance with the invention,

with a negative bias as compared with the ray, which bias is so adjusted that the ray in its stationary condition meets approximately against the centre of the image screen. The negative bias of the control plate may, in accordance with the invention, conveniently be replaced by a corresponding positive bias of the dynamically earthed deflecting plate (hereinafter referred to as earthed plate). In accordance with the invention, the positive bias is selected to be greater than the maximum control potential occurring at the control plate.

By reason of the arrangement according to the invention it is accomplished that the cross-current, viz., always a constant cross-current, flows ofi solely to the earthed plate, so that the control circuit remains completeiy unloaded.

The arrangement according to the invention permits, therefore, of the use of tilting generators, which possess high inner resistances.

Two forms of embodiment of the invention are shown by way of example in the appended drawimage screen it may be arranged in the conven tional manner. The anode is arranged under an angle with respect to the pair of deflecting plates i, so that the cathode ray when entering the system is directed against the control plate 3. The plate 4 is dynamically earthed at ll! over the condenser l and positively biassed against the earthed anode by means of the-potential source 9 through the medium .of a potentiometer 8. The control plate 3 is earthed at 6 over the scanning voltage generator ii. The ray is deflected by the scanning voltages in the direction to the positively biassed plate 5, the potentialof this plate being so chosen, that the ray in the stationary conditions meets approximately against the centre of the image screen.

Naturally the positive bias of the earthed plate A in relation to the anode 2 may also be produced in any other desired fashion.

Instead of disposing the anode'gecmetrically at an angle to the axis of the pair of deflecting plates, there may also be furnished between the anode and the pair of deflecting plates an element (for example, a deflecting condenser) producing a constant deflection of the ray.

An arrangement of this kind is shown in Fig. 2, in which like references have been given to corresponding members as in Fig. 1. In addition, 12 is the auxiliary deflecting condenser by which, in this modification of the invention, the cathode ray is caused to enter into the main pair of defleeting plates under an oblique angle. i is a direct current source by which the cathode ray is, in the stationary condition, redefiected into the axial direction.-

The auxiliary element l2 then alsorequires to be constructed and arranged in such fashion-that the cathode ray meets approximately against the centre of the control plate, or at least touches against the same.

The method according to the invention enables in simple fashion the production of television images which are entirely free of distortions produced by the cross-current error.

I claim: 7

1. In combination, a Braun tube, more particularly for television purposes comprising a cathode and an anode arranged in operative relationship thereto for producing a cathode beam, an image screen, a deflecting plate system mounted between said anode and said screen, means for supplying one of the plates of said system with alterhating deflecting voltages, means for dynamically earthing the other plate of said system, and means for causing any electron current produced in any circuit associated with said deflecting system by electrons not incorporated in said beam and attracted towards the parts of said system in the normal action of said tube to flow only to that one of said plates which is dynamically earthed.

2. In combination, a Braun tube, more particularly for television purposes comprising a cathode and an anode arranged in operative relationship thereto for producing a cathode beam, an image screen, a deflecting plate system mounted between said anode and said screen, a deflecting voltage generator of an inner resistance in the order of ohms for supplying one of the plates of said system with alternating deflecting voltages, means for dynamically earthing the other plate of said system, and means for causing any electron current produced in any circuit associated with said deflecting system by electrons not incorporated in said beam and attracted towards the parts of said system in the normal action of said tube to flow only to that one of said plates of said system which is dynamically earthed.

3. In combination a Braun tube, more particularly for television purposes comprising an evacuated envelope, a cathode, an anode arranged in operative relationship thereto for producing a cathode ray directed from said cathode to said anode, an image screen, a system of deflecting plates mounted between said anode and said screen, said anode being mounted at an angle to said deflecting plates system so that the cathode ray would, in the absence of further means for influencing the cathode ray direction, enter said deflecting system at an angle to the plates of said system and directed towards one of the plates, means for applying to'said anode a high positive potential relatively to said cathode, means for supplying the mentioned plate of said system with alternating deflecting potentials, means for dynamically earthing the other plate of said system, and means for applying to one of the plates of said system a bias relatively to said anode, said means for applying a bias being dimensioned to cause the bias to produce a stationary deflection of the cathode ray which causes the cathode ray to proceed, in the absence of alternating deflecting voltages, substantially in parallel to the plates of said system and substantially in the direction towards the centre of said image screen.

4. In combination a Braun tube, more particu larly for television purposes comprising an evacuated envelope, a cathode, an anode arranged in operative relationship thereto for producing a cathode ray directed from said cathode to said anode, an image screen, a system of deflecting plates mounted between said anode and said screen, said anode being mounted at an angle to said deflecting plates system so that the cathode ray would, in the absence of further means for influencing the cathode ray direction, enter said deflecting system at an angle to the plates of said system and directed towards one of the plates, means for applying to said anode a high positive potential relatively to said cathode, means for supplying the mentioned plate of said system with alternating deflecting potentials, means for dynamically earthing the other plate of said system, and means for applying to said other plate of said system a positive bias relatively to said anode, said means for applying a positive bias being dimensioned to cause the bias to produce a stationary deflection of the cathode ray which causes the cathode ray to proceed, in the absence of alternating deflecting voltages, substantially in parallel to the plates of said system and substantially in the direction towards the centre of said image screen.

5. In combination a Braun tube, more particularly for television purposes comprising an evac- V uated envelope, a cathode, an anode arranged in operative relationship thereto for producing a cathode ray directed from said cathode to said anode, an image screen, 'a system of deflecting plates mounted between said anode and said screen, said anode being mounted at an angle to said deflecting plates system'so that the cathode ray would, in the absence of further means for influencing the cathode ray direction, enter said deflecting system at an angle to the plates of said system and directed towards one of the plates, means for applying to said anode a high positive potential relatively to said cathode, means for supplying thementioned plate of said system with alternating deflecting potentials,

means for dynamically earthing the other plate of said system, and means for applying to the first mentioned plate of said system a negative bias relatively to said anode, said means for applying a negative bias being dimensioned to cause the bias to produce a stationary deflection of the cathode ray which causes the cathode ray to proceed, in the absence of alternating deflecting voltages, substantially in parallel to the plates of said systemand substantially in the direction towards the centre of said image screen.

6. In combination a Braun tube, more particularly for television purposes comprising an evacuated envelope, a cathode, an anode ar-' ranged in operative relationship thereto for producing a cathode ray directed from said cathode to said anode, an image screen, a system of deflecting plates mounted between said anode and said screen, said anode being mounted at an angle to said deflecting plates system so that the cathode ray would, in the absence of further means for influencing the cathode ray direction, enter said deflecting system at an angle to the plates of said system and directed towards one of the plates, means for applying to said anode a high positive potential relatively to said cathode, means for supplying the mentioned plate of said system with alternating deflecting potentials the maximum positive values of which are above the potential applied to said anode, means for dynamically earthing the other plate of said system, and means for applying to said other plate of said system a positive bias relatively to saidanode, which is higher than the diiierence between the maximum positive values of the alternating deflecting potentials applied to the first mentioned plate and the potential applied to said anode.

7. In combination a Braun tube, more partic,

'the plates of said system, means for applying to said anode a high positive potential relatively to said cathode, means for supplying the men tioned plate of said system with alternating deflecting potentials, means for dynamically earthing the other plate of said system, and means for applying to one of the plates of said system a bias relatively to said anode, said means for applying a bias being dimensioned to cause the bias to produce a stationary deflection of the cathode ray which causes the cathode ray to proceed, in the absence of alternating deflecting voltages, substantially in parallel to the plates of said system and substantially in the direction towards the centre of said image screen.

8. In combination a Braun tube, more particularly for television purposes comprising an evacuated envelope, a cathode, an anode arranged in operative relationship thereto for producing a cathode ray directed from said cathode to said anode, an image screen, a system of deflecting plates mounted between said anode and said screen, a deflecting condenser mounted between said anode and said deflecting plates system for directing the cathode ray towards one of the plates of said system, means for applying to said anode a high positive potential relatively to said cathode, means for supplying the mentioned plate of said system with alternating deflecting potentials, means for dynamically earthing the other plate of said system, and means for applying to one of the plates of said system a bias relatively to said anode, said means for applying a bias being dimensioned to cause the bias to produce a stationary deflection of the cathode ray which causes the cathode ray to proceed, in the absence of alternating deflecting voltages, substantially in parallel to the plates of said system and substantially in the direction to- Wards the centre of said image screen.

KURT SCI-ILESINGER. 

